gh-102500: Implement PEP 688 (#102521)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

4 files changed, 107 insertions, 2 deletions

diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 6b48334..a7803cf 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -169,7 +169,7 @@
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/vectorcall_limited.c _testcapi/heaptype.c _testcapi/unicode.c _testcapi/getargs.c _testcapi/pytime.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/pyos.c _testcapi/immortal.c _testcapi/heaptype_relative.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/vectorcall_limited.c _testcapi/heaptype.c _testcapi/unicode.c _testcapi/getargs.c _testcapi/pytime.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyos.c _testcapi/immortal.c _testcapi/heaptype_relative.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 
 # Some testing modules MUST be built as shared libraries.
diff --git a/Modules/_testcapi/buffer.c b/Modules/_testcapi/buffer.c
new file mode 100644
index 0000000..aff9a47
--- /dev/null
+++ b/Modules/_testcapi/buffer.c
@@ -0,0 +1,102 @@
+/* Test PEP 688 - Buffers */
+
+#include "parts.h"
+
+#include "structmember.h"           // PyMemberDef
+#include <stddef.h>                 // offsetof
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *obj;
+    Py_ssize_t references;
+} testBufObject;
+
+static PyObject *
+testbuf_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    PyObject *obj = PyBytes_FromString("test");
+    if (obj == NULL) {
+        return NULL;
+    }
+    testBufObject *self = (testBufObject *)type->tp_alloc(type, 0);
+    if (self == NULL) {
+        Py_DECREF(obj);
+        return NULL;
+    }
+    self->obj = obj;
+    self->references = 0;
+    return (PyObject *)self;
+}
+
+static int
+testbuf_traverse(testBufObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->obj);
+    return 0;
+}
+
+static int
+testbuf_clear(testBufObject *self)
+{
+    Py_CLEAR(self->obj);
+    return 0;
+}
+
+static void
+testbuf_dealloc(testBufObject *self)
+{
+    PyObject_GC_UnTrack(self);
+    Py_XDECREF(self->obj);
+    Py_TYPE(self)->tp_free((PyObject *) self);
+}
+
+static int
+testbuf_getbuf(testBufObject *self, Py_buffer *view, int flags)
+{
+    int buf = PyObject_GetBuffer(self->obj, view, flags);
+    Py_SETREF(view->obj, Py_NewRef(self));
+    self->references++;
+    return buf;
+}
+
+static void
+testbuf_releasebuf(testBufObject *self, Py_buffer *view)
+{
+    self->references--;
+    assert(self->references >= 0);
+}
+
+static PyBufferProcs testbuf_as_buffer = {
+    .bf_getbuffer = (getbufferproc) testbuf_getbuf,
+    .bf_releasebuffer = (releasebufferproc) testbuf_releasebuf,
+};
+
+static struct PyMemberDef testbuf_members[] = {
+    {"references", T_PYSSIZET, offsetof(testBufObject, references), READONLY},
+    {NULL},
+};
+
+static PyTypeObject testBufType = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    .tp_name = "testBufType",
+    .tp_basicsize = sizeof(testBufObject),
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
+    .tp_new = testbuf_new,
+    .tp_dealloc = (destructor) testbuf_dealloc,
+    .tp_traverse = (traverseproc) testbuf_traverse,
+    .tp_clear = (inquiry) testbuf_clear,
+    .tp_as_buffer = &testbuf_as_buffer,
+    .tp_members = testbuf_members
+};
+
+int
+_PyTestCapi_Init_Buffer(PyObject *m) {
+    if (PyType_Ready(&testBufType) < 0) {
+        return -1;
+    }
+    if (PyModule_AddObjectRef(m, "testBuf", (PyObject *)&testBufType)) {
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/Modules/_testcapi/parts.h b/Modules/_testcapi/parts.h
index d75412d..663d4f2 100644
--- a/Modules/_testcapi/parts.h
+++ b/Modules/_testcapi/parts.h
@@ -38,6 +38,7 @@ int _PyTestCapi_Init_Float(PyObject *module);
 int _PyTestCapi_Init_Structmember(PyObject *module);
 int _PyTestCapi_Init_Exceptions(PyObject *module);
 int _PyTestCapi_Init_Code(PyObject *module);
+int _PyTestCapi_Init_Buffer(PyObject *module);
 int _PyTestCapi_Init_PyOS(PyObject *module);
 int _PyTestCapi_Init_Immortal(PyObject *module);
 
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 1ecc442..38f4758 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -3959,7 +3959,6 @@ static PyTypeObject MyList_Type = {
     MyList_new,                                 /* tp_new */
 };
 
-
 /* Test PEP 560 */
 
 typedef struct {
@@ -4310,6 +4309,9 @@ PyInit__testcapi(void)
     if (_PyTestCapi_Init_Code(m) < 0) {
         return NULL;
     }
+    if (_PyTestCapi_Init_Buffer(m) < 0) {
+        return NULL;
+    }
     if (_PyTestCapi_Init_PyOS(m) < 0) {
         return NULL;
     }